Studies are being carried out to determine if steady-state infusion of the short acting opioid antagonist naloxone or chronic treatment with the longer-acting antagonists nalmefene or naltrexone prevents the neuroendocrine and immunological perturbations caused by acute or bolus administration of these agents and thus to determine the extent of function of endogenous opioids in endocrine physiology. also studies are being performed to develop the effects of various opiates, opioids, and ethanol on endogenous and immune function.